Liquid fuel injection pumps



1969 P. e. WARWICKER ETAL 3,481,272

LIQUID FUEL INJECTION PUMPS Filed Jan. 8, 1968 /X//////I/ lll United States Patent 6 39/67 Int... Cl... 39 b. 9/1 4.9/00

rte-as C a m ABSTRACT OF THE DISCLOSURE The invention relates to liquid fuel injection pumps of the kind comprising a pump plunger movable in one direction to discharge fuel'from a pumping chamber by the action of a fluid pressure operable piston, the extent of movement of the piston and therefore the plunger being under the control of passage means formed in the piston and co-operating with a supply port 23 formed in the cylinder wall.

This invention relates to liquid fuel injection pumps for supplying fuel to a combustion space of an internal combustion engine and of the kind comprising in combination, a pump plunger which during movement in one'direction displaces fuel from a pumping chamber to the engine and a fluid pressure operable piston contained within a cylinder for moving said plunger in said one direction, said cylinder being arranged to receive fluid under pressure from a source in timed relationship with the engine.

The object of the invention is to provide such a pump in a simple and convenient form.

According to the invention, the fluid under pressure is admitted to the cylinder through passage means formed in the piston and which co-operates with a fluid pressure supply port in the wall of the cylinder, the communication between the passage and the supply port being arranged to be broken when the piston has been moved a predetermined distance.

In the accompanying drawings:

FIGURE 1 is a sectional side elevation of one example of a fuel injection pump in accordance with the invention, and

FIGURE 2 is a view of a modification of part of the apparatus of FIGURE 1.

Referring to the drawings, there is provided a pumping plunger 10 which is accommodated within a cylindrical bore formed in the body part of the pump. The inner end of the bore is in communication with an outlet 11 and for controlling the flow of fuel through this outlet there is provided a non-retum delivery valve 12. In use, the outlet is connected to a fuel injection nozzle indicated at 13 which is arranged to direct fuel into a combustion space of an engine with which the pump is associated.

Formed in the wall of the bore is a spill port 14 which is in communication with a fuel supply passage 15 formed in the body part and which, in use, is connected to a source of liquid fuel. On the periphery of the plunger is a helical groove 16 which is in communication with the pumping chamber defined by the bore. In use, during inward movement of the plunger fuel is expelled from the pumping chamber by way of the outlet 11 until the helical groove 16 is exposed to the spill port 14 whereafter the delivery of fuel to the engine ceases and the remaining fuel in the pumping chamber is expelled through the spill port. During outward movement of the plunger as soon as the port is uncovered fuel from the supply flows into the pumping chamber and completely fills same.

The plunger is loaded in the outward direction by means of a coiled compression spring 17 and for moving the plunger inwardly against the action of the spring, a fluid pressure operable piston 18 is provided. This is located within a cylinder 19 which may be formed in the body part or in a part adapted to be secured thereto.

There is also provided a source 20 of fluid under pressure and this may comprise a pump which is driven by the engine and which supplies fluid to an accumulator. Fluid under pressure is supplied to the cylinder under the control of a valve 21 which is operated in timed relationship to the engine and the arrangement is such that when the 'valve is opened fluid under pressure acts on the piston to effect inward movement of the plunger.

Such systems are fairly well known and one of the problems with such a system is the fact that as soon as the spill port 14 is opened to the helical groove 16, the force restraining the inward movement of the plunger and piston is reduced with the result that rapid acceleration occurs and the plunger and piston attain a high velocity and eventually must be stopped either by positive stops or by means of dash pots.

In the present system, the fluid under pressure is admitted through the cylinder by way of a passage 22 formed in the piston 18 and which is in registration with a port 23 formed in the wall of the cylinder 19. It is arranged that after the piston has moved a predetermined distance, the passage 22 moves out of registration with the port 23 thereby to cut off the supply of fluid under pressure to the cylinder. Moreover, it is arranged that the cylinder is closed so that a partial vacuum occurs in the cylinder and this assists the retardation of the piston and plunger.

In order to allow the piston 18 and plunger 10 to return under the action of the spring 17 a port 24 in the wall of the cylinder 19 is opened to a drain by means of a valve 25. This valve is coupled to the valve 21 and as shown when the valve 25 is closed the valve 21 is open and vice versa. If desired a further spring 26 may be provided to assist the return motion of the piston 18.

In the system described the quantity of fuel supplied through the outlet 11 is determined in the conventional manner, by adjusting the angular setting of the plunger so that the pressure in the pumping chamber is relieved earlier or later in the stroke of the plunger as desired. The stroke of the piston 18 is fixed so that for each injection stroke no matter what quantity of fuel is being supplied, the quantity of fluid delivered by the source 20 is constant. If only a small quantity of fuel is being supplied then there is a wastage of fluid so that an excessive amount of power is required to operate the system.

In order to minimize the wastage of fluid the stroke of the piston 18 is variable. This is achieved by forming the end of the passage 22 where it breaks out onto the wall of the piston, as a circumferential groove 27. The lower edge of the groove as is shown in FIGURE 2, is inclined and a rack bar 28 is provided whereby the angular setting of the piston 18 can be adjusted without upsetting its ability to move axially. The rack bar 28 is coupled to the rack bar 29 of the fuel pump so that the two move in synchronism it being arranged that the piston stops a short distance after the spill port 14 has opened to the helical groove.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. A liquid fuel injection pump for supplying fuel to a combustion space of an internal combustion engine and comprising in combination, a pump body part in which is defined a cylindrical bore, an axially movable and angularly adjustable plunger, an outlet from the bore, a spill port formed in the wall of the bore, a shaped spill groove formed in the plunger for co-operation with said spill port, said plunger during movement in one direction serving to displace liquid fuel at high pressure through the outlet from the bore until the spill groove registers with the spill port, a liquid pressure operable piston contained within a cylinder for moving said plunger in said one direction, a liquid pressure supply port formed in the wall of said cylinder and communicating in timed relationship with the engine, with a source of high pressure liquid, passage means formed in said piston, said passage means communicating with said cylinder and breaking out on the wall of said piston in a position to communicate with said port, the communication of said passage means with said port being broken after the piston has moved a predetermined distance in said one direction thereby to create an hydraulic lock in said cylinder to halt the movement of the piston.

22. A liquid fuel injection pump as claimed in claim 1 including valve means operable in synchronism with the associated engine for controlling the flow of liquid under pressure through said port.

3. A liquid fuel injection pump as claimed in claim 2 including further valve means operable to permit liquid to escape from said cylinder, said further valve means and said valve means being coupled together so that when one valve means is open the other is closed.

4. A liquid fuel injection pump as claimed in claim 3 including a circumferential groove formed on the periphery of the piston for registration with said supply port, said groove being in communication with said passage means, the trailing edge of said groove being inclined, and means for adjusting the angular setting of the piston whereby to control the travel of the piston.

5. A liquid fuel injection pump as claimed in claim 4 in which said means comprises an adjustable rack bar engaging with teeth formed on the piston.

References Cited UNITED STATES PATENTS 1,955,383 4/1934 Hermann 10337 1,956,612 5/1934 Brun 10350 2,033,579 3/1936 Koster et a1 10337 2,810,375 10/1957 Froehlich et a1. 103-37 WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 

